How MyCat Simplifies Database Sharding and Read/Write Routing

MyCat is a database middleware that enables easy database sharding and read/write routing, reducing business code complexity.

Evolution of Database Architecture

1. Single Database Architecture

In early projects, all modules (registration, login, shopping) share one database, leading to performance bottlenecks as traffic grows.

2. Distributed Deployment

Adding multiple application servers distributes load, but a single database still becomes a bottleneck; a cache layer is added to reduce DB queries.

3. Master‑Slave Architecture

Introducing a master for writes and a slave for reads separates read/write traffic.

public User selectUser() {
    readTemplate.selectById(...);
}
public User insertUser() {
    writeTemplate.insert(user);
}

4. Vertical Sharding

Each business module gets its own application and independent database, eliminating cross‑module impact and single‑DB pressure.

5. Horizontal Sharding

Large tables (e.g., User) are split into many tables (User_000 … User_999) based on userId % 1000, distributing data across multiple databases.

MyCat can automatically route queries to the correct shard using configured sharding rules, removing the need for manual data‑source selection in code.

public User selectUser() {
    dataTemplate.selectById(...);
}
public User insertUser() {
    dataTemplate.insert(user);
}

Beyond routing, MyCat supports master‑slave failover, unified connection handling, and other middleware functions, allowing projects to focus on business logic.